Production of fine metallic wires directly from molten metal would be desirable to reduce production costs. Furthermore, if such a fine metallic wire has an amorphous structure, it will have a great possibility of being put into practical use in a wide variety of fields, such as for electric and electromagnetic parts, composite materials, and fibrous materials, since it has excellent chemical, electromagnetic, and physical properties. In particular, an amorphous metal is superior in mechanical properties to a crystal alloy which is in commercial use; for example, it has a greatly high strength, and is free from work hardening and is high ductile. It has therefore been desired to produce high quality fine amorphous metallic wires which are circular in cross-section and are freed of mottles in size.
Typical methods which have heretofore been proposed to produce fine amorphous metallic wires having a circular cross-section directly from molten metal include (a) a method in which a molten metal is drawn and cool-solidified in a state such that it is covered with glass, utilizing the stringiness of glass (Taylor Process), (b) a method in which a molten metal is jetted from a nozzle into a cooling fluid by the utilization of gravity, etc., and is cooled and solidified therein (which was proposed by Kavesh et al.), and (c) a method in which a cooling liquid medium is introduced into a rotary drum and is used to form a liquid layer on the inner walls of the drum by the action of centrifugal force, and a molten metal is jetted into the liquid layer and is cooled and solidified therein.
In accordance with method (a), however, since the molten metal is covered with glass and air-cooled, the cooling rate is slow, and only fine amorphous wires of small wire diameter can be obtained. Furthermore, since it is composite spinning, the structures of the melting and spinning zones are complicated, and high precision is required. Moreover, it is necessary to remove the glass coating prior to the use as a fine metallic wire.
In accordance with the method (b), it is difficult to control the flow rate of the cooling fluid and to increase the spinning rate, and therefore it is very difficult to produce continuous fine amorphous metallic wires of high quality.
The method (c) is a practical method which is a considerable improvement as compared with the above two methods (a) and (b). In accordance with the method (c), it is possible to control the rate of the cooling liquid and the disturbance thereof, and furthermore, since the stream of molten metal is cooled and solidified by passing it through the rotary cooling liquid by the resultant force of jetting pressure and centrifugal force, the cooling rate is very fast compared with those for the methods (a) and (b), permitting the production of fine amorphous metallic wires of very high wire diameter. However, fine amorphous metallic wires produced directly from an alloy having an amorphous substance-forming ability only by molten spinning have mottles (variations) in size in the longitudinal direction thereof and are not round in cross-section, and therefore, they cannot sufficiently exhibit the features that they possess inherently.
There is known a method in which a fine metallic wire is drawn to improve the uniformity of morphology and mechanical properties. The conventional drawing method, however, incidentally requires special treatments such as planting for coating and heating before and after working, and therefore, it is not a convenient method at all. Furthermore, in the conventional technique, to draw the fine crystal metal wire, it has been the practice to conduct the wire-drawing processing repeatedly, making the sacrifice that the procedure becomes complicated since as the wire-drawing processing is repeated, the mechanical properties are improved.
It is also known, as described in Nippon Kinzoku Gakkai Shi (Journal of the Japanese Learned Society of Metals), Vol. 44, No. 9, pp. 1084 to 1087 (1980), that a ribbon of amorphous metal can be drawn to make its cross-section circular. This method, however, only has the effect of making the cross-section circular, and does not improve the mechanical properties.
In addition, Materials Science and Engineering, pp. 41 to 48, 38 (1979) describes the drawing of fine amorphous wires comprising a Pd.sub.77.5 Cu.sub.6 Si.sub.16.5 alloy system. When a fine wire is used having a breaking strength: .sigma..sub.F =148.+-.4 kg/mm.sup.2 and a degree of drawing at break: .epsilon..sub.F =2.27.+-.0.16%, even if the fine wire is drawn until the area reduction percentage reaches 44%, the breaking strength (.sigma..sub.F) and degree of drawing at break (.epsilon..sub.F) of the drawn fine wire are 158.+-.5 kg/mm.sup.2 and 2.58.+-.0.11%, respectively. Thus, the drawn fine wire is improved only by 6.8% and 13.7% in the breaking strength and degree of drawing at break, respectively, and it fails to have excellent mechanical properties. Furthermore, the Pd.sub.77.5 Cu.sub.6 Si.sub.16.5 alloy system is very expensive and is not suitable for practical use.